Frequency changing system



Aug. 14, 1934. L. A. GEBHARD ET AL FREQUENCY CHANGING SYSTEM Filed June 21, 1933 2 Sheets-Sheet l 1934. A. GEBHARD ET AL 1,969,746

FREQUENCY CHANGING SYSTEM Filed June 21, 1933 2 Sheets-Sheet 2 Patented Aug. 14, 1934 FFlC E 1,969,746 FREQUENCY CHANGING SYSTEM Louis A. Gebhard and Corrie F. Rudolph,

Washingto Application June 21, 1933, Serial No. 676,950 9 Claims. (01.171442) (Granted under the act of March 4 amended April 30, 1928; 370 0.

Our invention relates broadly to high frequency signal ion systems and more particularly to frequency changing apparatus for high frequency signal transmission systems.

5 One of the objects of our invention is to provide a construction of frequency changing apparatus having a high degree of efliciency and adapted particularly for operation in push-pull amplification systems in high frequency trans-' mitters.

Another object of our invention is to provide a construction of adjustable inductance system for use in balanced electron tube circuits of high frequency transmitters having means for equalizing the circuits of the balanced electron tube systems for any inequalities which may tend to unbalance the balanced relationship of the amplification ssytem.

Still another object of our invention is to provide a construction of double continuously variable inductance having a common control for simultaneously adjusting each of the inductances with means for independently adjusting one of the inductances with respect to the other for effecting a balance in the circuits in which the inductances are connected.

Still another object of our invention is to provide a construction of mechanical control system for effecting a simultaneous control of a pair lot inductance units in a balanced electron tube amplifier system for the independent control of one of the inductance units for equalizing any conditions of unbalance which may be found to exist in the electron tube circuits in which the inductances are connected.

A further object of our invention is to provide an inductance system for electrical connection in the high frequency transmission circuits of a balanced amplifier system where the inductance is provided with adjusting means for correcting for inequalities which may exist in the electron tubes or in the electrical elements connected in the amplification circuits for insuring maximum efllciency of operation of the balanced system. 4

A still further object of our invention is to provide a construction of clutch system which is disposed intermediate two switching members, each establishing variable electrical connection with the turns of a pair of inductance units with means for rotatably driving both of the switching members simultaneously through the said clutch 'or releasing the clutch for driving one of the switching members independently of the other switching member for equalizing the effec- 3, 1883, as G. 757) tive inductances which may be employed in balanced electron tube circuits connected with the inductance units.

Other and further objects of our invention reside in the construction of an inductance system so for high frequency amplification circuits as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

Figure 1 'is a vertical sectional view taken through an inductance system constructed in accordance with our invention with parts shown in side elevation; Fig. 2 is an enlarged cross sectional view of the clutch system employed in transmitting rotary movement to the switching members which electrically connect with the two inductance units in a balanced electron tube amplification system; Fig. 3 is a cross sectional view taken through the control shaft of the frequency changing system on line 3-3 of Fig. 2; Fig. 4 is a view showing the parts constituting the clutch mechanism in position ready for axial assembly; Fig. 5 is an elevational view of the clutch control shaft removed from the inductance system; and Fig. 6 is a circuit arrangement of a high frequency balanced electron tube frequency amplification system showing one of the applications of the inductance system of our invention. In high frequencyelectron tube amplification systems it is customary to arrange the electron tubes in balanced or push-pull relationship. In order to obtain maximum eiliciency in such amplifiers, it is important that a true. balanced relationship be maintained. Such balanced relationship, however, is difllcult to obtain under practical conditions by reason of minute differ ences which exist in electron tube constructions and the difficulty of precisely matching the electron tube in one side of the balance system by an electron tube in the other side of the balance system. The other elements of the push-pull circuit also vary in minute degrees, tending to disturb the balance of the amplification circuit Moreover conditions arise where it is necessary to substitute an electron tube in one side of the balance circuit for an electron tube whose life has been fully expended, and in effecting such substitution. the replacement tube often has characteristics which are not identical with the characteristics of the other tube in the balance system, thereby introducing inequalities and conditions of unbalance which tend to reduce the efiiciency of the operation of the electron tube system. Our invention provides an inductance system having means for eliminating these un- I10 desirable eflects by the provision of a continuously variable inductance system which is divided into two portions with the separate portions electrically connected in the respective circuits of the electron tubes constituting the balanced. am-

plifier. -In order to control the effective inductance in the respective electron tube circuits we provide a two element switching system controlled by the rotary shaft member. A special construction of clutch divides the rotary shaft member into two portions, the clutch being operative from a position adjacent the control .position of the rotary shaft. By releasing the clutch it is possible to adjust one of the elements of the switching system independently of the other to a position where the electron tube circuits are precisely balanced, in which positions the elements of the switching system may be again interlocked for simultaneous adjustment and the change of .the frequency characteristics of the electron tube circuits equally for equal angular displacements of the control shaft through the inductance system. In the event that other inequalities occur during the operation of the ampliflcation system, the clutch may be again released for the independent adjustment of one switching element with respect to the other and the locking of the switching elements for con-' tinued frequency control ofthe circuits of the electron-tubes constituting the push-pull system.

Referring to the drawings in more detail, reference character 1 designates the front panel of a radio transmitter behind which there is mounted an insulated panel 2 which forms an end support for the insulation strips 3 which are slotted to receive the conductive strip constituting .the inductance 4 and the conductive strip constituting the inductance 5 disposed in spiral relation about the axis of the inductance coils The inductance coils 4 and 5 are spaced centrally of the frame constituted by insulation strips 3, as represented at 6. The ends of the inductances4 and 5 are interconnected, however, as represented by the longitudinally extending bus bar 7 which provides an interconnection for the intermediate ends of inductance units 4 and 5 through a lug connector as at point 8. One end of the inductance 4 is brought out to a terminal 9 which is supported on rod 10. We have not illustrated the opposite end of the inductance 5 but it will be understood that provision is made for the proper mounting of the terminal which is connected to the extreme end of the inductance 5 in a manner similar to the arrangement of terminal 9. A frame member 11 is supported by suitable mounting means 12 with respect to the frame of the inductance system shown at 2 for providing means for journaling the telescopically disposed rotatable sleeves 14 and 15.

The frame member 11 is provided with sleeve or bushing 16 which extends on an axis normal to the frame member 11 and provides a journal for the rotatable sleeve 14. The rotatable sleeve 14 projects beyond the frame member 11 and is provided with a spacing member 1'7 thereon which spaces the sleeve 18 in bevel gear 19 from frame member 11 for allowing free rotation of the bevel gear 19 intermeshed with the bevel gear shown in dotted lines at 20. Sleeve 18 is pinned to the rotatable sleeve 14 by a suitable means such as pin 21 to insure simultaneous rotation of gear 19 with the sleeve 14. The drive gear 22 is carried by sleeve 18 in intermeshed relation with pinion 23 which is carried by shaft 24 journaled in sleeve 25-supported in frame member 11. We

provide a coupling member 26 connected with the end of stub shaft 24, which coupling member is connected through coupling member 27 with shaft 28 which ismanually driven from crank 29 from th e front of panel 1. The rotatable sleeve 15 carries bevel gear 30"keyed thereto by suitable means as represented at 31. The bevel gear 30 meshes with the bevel gear 26 so that rotation of rotatable sleeve 14 is accomplished by rotation of rotatable sleeve 15 in the opposite direction. A gear housing 32 is provided over the. bevel gear 30 for enclosing the gear 30 and also providing a means of support for rod member 10 which supports the terminal 9 to which one end of the inductance 4 is electrically connected. Rotatable sleeves 14 and 15 are rotated in opposite. directions, sleeve 15 moving concentrically over sleeve 14. A switch member 33 carried by switch arm 34 mounted on the slidable support .35 is engaged over the sleeve 15. The slidable support 35 is free to move longitudinally along sleeve 15 under control of pin 36which projects therethrough in a radial direction and passes through the slot 37 in rotatable sleeve 15. The conjoint movement of rotatable sleeves 14 and 15 in opposite directions, results in the driving of switch member 33 to selected angular positions 101'. controlling the effective number of turns in the inductance 4.

The end of the rotatable sleeve 14 is provided with a frusto-conical recess 38 therein and a cylindrical recessed portion 38a adjoining the axial bore 14a which extends through the sleeve 14. The frusto-conical recess 38 has a spring device 39 disposed therein against which, the frusto-conical member 40 is adapted to yieldingly engage. The frusto-conical member 40 is carried by a plate member 41 mountedby suitable securing means such as screws 42 on insulated block 43. Insulated block 43 forms a coupling member for driving the sleeve 44 whichis pinned to rotate with the rotation of block 43 by means of pin member 45 extending through the projecting stub shaft 46 secured to block 43 by plate member 47. The sleeve 44 is rotatable over the fixed screw member 48. Screw member 48 'is fixed to the opposite end of the frame structure of the inductance system and is provided with a spiral groove 49 into which the pin member 50 extends. The pin member 50 is carried by the sleeve member 51 which is movable over the sleeve 44 to move switch members 52 to selected positions of adjustment along the; tension of inductance 5. The switch member' 52 carried by bracket 53 supported by sleeve member 51 for selectively including the desired number of turns of inductance 5 in the amplification circuit. In order to change the frequency adjustment of the inductances 4and 5 connected in the input circuits of electron tubes 54 and 55, as shown 52. During this driving operation, as heretofore 1" described, the tachometer or counter 56 is connected in geared relation to the shaft 28 so that the precise position of the switches 33 and 52 can be determined at all times and these switches can be restored to desired positions for particthe frusto-conical mits simultaneous driving of described and has sideration of Fig. 5. A rod member 57 screwthreaded at 58 extends axially through the bore 14a in rotatable sleeve 14. The end 59 of rod member 57 is enlarged and is secured in the recessed end of the insulated sleeve member 60. The insulated sleeve member 60 extends through an aperture in the panel 1 and is provided with an actuating knob 61 thereon operative from the front of the panel. The control knob 61 is revolved to screw the screw threads 58 into the screw-threaded recess 40a of member 40 to provide a tight frictional connection between frusto-conical member 40 and the frusto-conical recess 38 against the action of spring device 39. This perswitch members 33 and 52. However, when it is desired to release switch 33 for independently adjusting the position of switch 52 the knob 61 is rotated to loosen screw threads 58 with respect to screw threads 4011. Spring device 39 operates to force frusto-conical member 40 out of engagement with frusto-conical recess 38 thereby preventing the further transmission of driving torque from rotatable sleeve 14 to the coupling device 43 or sleeve 44. When the clutch is thus disengaged, switch 33 remains stationary while switch 52 may be independently adjusted. This permits an equalization to be made of the excitation voltages in the two halves of the high frequency amplification system. That is to say, by disengaging the clutch and driving switch 33 alone, switch 52 may be displaced in any desired amount and direction to effect proper division in the excitation voltages of the circuits of electron tubes 54 and 55, as shown in Fig. 6. That is to say, different angular displacements of the switches 33 and 52 may be desirable with respect to the inductance coils 4 and 5 for permitting the equal division of the exciting energy in the push-pull amplifier circuits. 3

We have shown the push-pull amplifier circuits diagrammatically in Fig. 6 wherein the grid electrodes 54a and 55a connect to the opposite ends of the inductance coils 4 and 5. The cathodes of each of the tubes are shown schematically at 54b and 55b heated through transformer systems 62 and 63. Balanced condensers are diagrammatically represented at 64 and 65. The potential for grid excitation is introduced across terminals 66. The potential for plate circuit energization is introduced across terminals 67. The output circuit leading from anodes 54c and 550 is connected to opposite ends of the output inductance system and coupling coil 68. This apparatus is a duplicate of the inductance system heretofore been shown in the same diagrammatic manner.

By reason of the audible adjustment of switching element 33 which is permitted with respect to switching element 52 a precise balancing of the circuits of the push-pull amplifier system may be effected for obtaining an accurate division of the excitation current in the balance circuits for maintaining a high degree of efficiency in operation. By reason of the independent adjustment of the switching members in the high frequency inductance system of our invention, tubes having such diverse characteristics as are normally found 1 in commercial tolerances may be employed with 3 a high degree of efliciency in high frequency transmission circuits.

While we have described our invention in one of its preferred embodiments, we desire that it purposes without the payment of any royalty coupling means for driving one of said switch members independently of the other of said switch members.

3. A high frequency inductance system comprising a pair of inductance units mounted end to end in spaced relation, a rotatable shaft system comprising a ductance, insulation means disposed between said shaft members and means for coupling said shaft members for driving said switch members simultaneously, or alternatively, releasing said shaft members for driving one of said switch members Iiandependently of the other of said switch memera.

4. A high frequency inductance system comprising a pair of inductance units mounted in spaced relation end to end, a rotatable rotatable member, a switch member slidably and rotatably carried by each of said rotatable members, insulation means disposed between the ends of said rotatable members, and a clutch for interconnecting said rotatable members through said insulation means for effecting a simultaneous driving operation of each of said switch members, or alternatively, driving one of said switch members independently of the other of said switch members.

5. A high frequency inductance system comprising a pair of inductance units disposed end to end, a rotatable shaft system extending through said inductance units and including a pair of separable rotatable portions, a shaft member engaging each of said rotatable portions, insulation means disposed between the ends of the rotatable portions of said shaft system, and a taneously driving clutch'member operative from one end of said inductance system for interconnecting the rotatable portions of said shaft system said switch members, or alternatively, disconnecting one of said rotatable portions with respect to the other of said rotatable eiiecting an adjustment of one of members independently of the adjustment of the other of said switch members.

6. A high frequency inductance system com- .prising a pair of inductance units disposed end terconnecting said rotatable portions for effect-v ing simultaneous adjustment of said switch members, or alternatively, releasing said clutch for effecting independent adjustment of one of said switch members with respect to the other switch member.

'7. A high frequency inductance system comprising a pair of coextensive inductance units, a rotatable shaft system extending axially through said inductance units and comprising axially aligned rotatable portions individual to each of said inductance units, insulation means for coupling the rotatable portions of said shaft system, a clutch interposed between said insulation means and one of the rotatable portions of said shaft system, a switching member carried by each of the rotatable portions of said shaft system and engageable with the turns of said inductance units, and an actuating member extending through one of the rotatable portions of said rotatable shaft system and engaging the clutch adjacent said insulation means for establishing a through connection between the rotatable portions of said rotatable shaft system for simultaneously driving said switching memfor simulbers, said means being releasabl independent adjustment of one of members with respect to the other.

8. A high frequency inductance system comprising a pair of coextensive inductance units, a rotary shaft system extending axially through said inductance units and including a pair of separable portions individual to each of said inductance units, insulation means disposed between theseparable portions of said rotatable shaft system, a clutch comprising a frusto-conical shaped member carried by said insulation means and a frusto-conical recess in one end of one of said separable portions, a switch member carried by each of said separable portions and engaging the turns of the respective inductance units, means for establishing binding frictional engagement between the faces of the frustoconical member and the frusto-conicalrecess for simultaneously driving both of said switch members, and means for releasing the frictional engagement between the faces of said frustc-conical member and said frusto-conical recess for eifecting independent adjustment of one of said switch members with respect to the other of said switch members.

for permitting said switch 9. A high frequency inductance system comprising a pair of coextensive inductance units, a rotatable shaft system comprising a pair of axially aligned members, a s 'tch carried by each of said members and engaging the turns of the respective inductance units, said members each comprising a pair of concentrically disposed elements, the inner element in one of said members having a longitudinally extending bore therein, a rod member extending through the bore in said element, an insulated coupling disposed between said members, a clutch having one element thereof carried by said insulated coupling, the screwthreaded end of said rod member being engageable for interconnecting said clutch with the coacting face of said switches may be driven simultaneously, said rod being rotatable for releasing said clutch for allowing adjustment of one of said switches independently of the other of said switches.

LOUIS A. GEBHARD. CORRIE F. RUDOLPH.

the adjacent member whereby 

